Within some conventional drills of the aforenoted type, such as those described for example in FR 1 588 841 (HILTI), these balls, or cylinders, provide not only locking of the components in the axially extending sliding mode but also locking of the same in the rotational mode of driving device.
Within other conventional drill systems, such as those described in FR-A-76 34 195 (BOSCH) the tool-holder includes at least one rotational driving device in the form of a key.
It can be seen that the bits used within the drills of the first type (HILTI) do not have axial grooves provided upon their shanks and therefore cannot be used within drills of the second type (BOSCH).
The purpose of the invention is precisely to make it possible to use either a bit provided with a drive groove or a bit not provided with a drive groove within the same tool-holder.
It is known from European Patent Application 0 223 738 which corresponds to DE 35 39912 that this result can be obtained by providing within the wall of the tool-holder radially open cavities of different shapes which respectively correspond to a locking ball or cylinder and to a driving element in the form of a key and a setting casing which is adapted to cause radial introduction into the cavities or to permit the escape from the cavities the corresponding ball or driving element.
As can be appreciated, this type of structure is quite complicated and therefore relatively expensive.